In general, various kinds of tubes for accommodating gas or liquid therein are typically formed with only one cell. If necessary, a plurality of cells may be formed in the tube by dividing the tube into the multiple cells.
In all cases, the single cell should have at least one inlet (or inlet and outlet). Further, if the single tube is divided into the multiple cells, it is common that each cell is constructed to have one inlet belonging thereto.
For example, a bolster constructed to accommodate air therein can be manufactured such that an entire tube T of the bolster is formed with a single cell as shown in FIG. 17 or is divided into a plurality of cells as shown in FIG. 18. At this time, it is apparent that a single air inlet V is formed in the single-cell tube while each cell of the multi-cell tube has a single air inlet V belonging thereto.
In use, in a case where the entire tube T of the bolster is formed with only one cell as shown in FIG. 17, it is easy to let the air into or out of the tube. However, when a user rests his/her head on the bolster, air residing in a portion of the tube pressed down by his/her head is moved to the other portions of the tube. Thus, there is a problem in that the bolster does not fulfill its own proper function. In particular, if any portion of the tube bursts open, whole air in the tube leaks out, and thus, an inherent function of the bolster is completely lost.
In addition, in a case where the tube T is formed with the plurality of cells as shown in FIG. 18, it is inconvenient in that the air should be let into and out of the respective cells one by one. However, when the user rests his/her head on the bolster, the air residing in the portion of the tube pressed down by his/her head is moved to the other portions of the tube. Thus, there is convenience of use in that the head is not rocked. Furthermore, even though any portion of the tube bursts open, all the whole air in the tube does not fully leak out, and thus, the bolster does not completely lose its own inherent function.
Similarly, the above principle is also applied to a tank other than the tube.
For instance, in a case where an oil tanker is formed with a tank having a single cell for accommodating oil therein, it is very convenient to let the oil into and out of the tank, but the whole quantity of the oil within the tank inevitably leaks out when the oil begins to leak out in an emergency. Alternatively, in a case where the tank of the oil tanker is formed with a plurality of divided cells, the other cells are kept airtight even though any one cell is broken. Thus, a relatively small amount of oil can leak out from the tank, but it is very inconvenient to let the oil into and out of the tank.